Sunita Williams Witness 16 Sunrise and Sunsets Every Day on ISS | Here’s Why

Astronauts aboard the International Space Station (ISS) experience a unique phenomenon—sunrise and sunset not just once a day, but as many as 16 times. For those living in space, such views become a regular part of life, with NASA astronaut Sunita Williams offering a personal account of this spectacular experience.

The Science Behind 16 Sunrises and Sunsets

Orbiting Earth at a speed of approximately 28,000 km per hour, the ISS completes a full orbit every 90 minutes. This rapid speed means that astronauts experience a sunrise or sunset approximately every 45 minutes. Each orbit brings them from the dark side of Earth to the sunlit side and back again, allowing astronauts to witness a phenomenon most people only observe twice a day.

In 2013, during a felicitation ceremony at the University of Gujarat in the presence of then Chief Minister Narendra Modi , Williams shared her fascinating experience of witnessing multiple sunrises and sunsets. “Because I had wanted to go to space and worked hard for it, I was lucky to see 16 sunrises and 16 sunsets in a day in a fast-moving space shuttle,” the seasoned astronaut recalled.

A New Day-Night Rhythm in Space

Unlike life on Earth, where a typical day consists of about 12 hours of light and 12 hours of darkness, astronauts aboard the ISS live through a much faster cycle. They experience 45 minutes of daylight followed by 45 minutes of darkness, creating a continuous rhythm of day and night that repeats 16 times within a single Earth day.

How Astronauts Mark time in Space

In space, traditional day-night rhythms don’t apply, as astronauts circle the planet every 90 minutes. Without the natural cues of sunlight, astronauts on the ISS follow Coordinated Universal Time (UTC) to structure their schedules. Their routines are highly regimented, with work, meals, and rest scheduled in five-minute intervals. This disciplined structure is essential for maintaining both physical and mental health in the microgravity environment of space.

To stay synchronised with mission control on Earth, astronauts rely on atomic clocks, which provide extreme precision for tasks like navigation, especially for missions beyond Earth's orbit. These timekeeping devices are crucial for the success of space missions, ensuring astronauts maintain alignment with Earth-based operations.

When Will Sunita Williams Come Back? 

Williams’ current mission has been extended due to delays in the Boeing Starliner spacecraft’s return schedule, keeping her in orbit until February 2025. Alongside fellow astronaut Butch Wilmore, she is using this additional time to contribute to critical research and explore the unique experiences space has to offer, including the ability to witness several sunrises and sunsets within just one Earth day.